This is a proposal to establish an Electron Spin Resonance Center at the University of Illinois, Urbana-Champaign, as a Research Resource. The establishment of the Center capitalizes on the existing major ESR equipment and expertise and will greatly enhance the instrumental capabilities available for biomedical research both locally and nationally. The existing instrumentation to be included in the resource consists of four 9GHz, one 35GHz, and one 1-2GHz spectrometers, and an ENDOR system. The core research and development activities will center on the development and improvement of two additional types of spectrometers that are not available to most of the biomedical research community: an Electron Spin Echo ESR spectrometer and a Very High Frequency (3mm, 95GHx) ESR spectrometer. Neither type of instrumentation currently is available either commercially or in any generally accessible user center. These instruments have considerable potential for solving a wide array of biomedical problems and their development in the Center will provide a very cost-effective way to make them available to many potential users. In addition to the development of the instruments themselves, the proposed resource will develop their applications to biochemical and biological problems. Development of computer support for biomedical studies for direct spectroscopy, spectroscopic analysis, and spectral simulation will also be part of the core research program. The emphasis of the collaborative studies and service activities of the resource will be to provide support for investigators with modest experience in ESR as well as those with extensive ESR experience and expertise. The development and operation of the resource will include input by prominent ESR spectroscopists from other institutions, including the National Biomedical ESR Center in Milwaukee. Educational activities will include direct training of students, postdoctoral fellows, and visiting fellows as well as workshops in both general ESR technology and the specialized instrumentation of the Center at the University of Illinois.